Fall 2016

The Standard Model of particle physics is oft referenced, but rarely explictly defined. In our standard introductory lecture, we come together to construct a general talk with the background in the parts of the standard model we are most interested in.

The German Enigma Machine represented a giant leap forward in military message encoding. In order to decode messages sent around with these machine British codebreaker at Bletchley park had to develop novel techniques for how to decode these messages. This talk will provide a bit of an overview of how this was done and discuss not just how the decoding was performed but also how it was used to help shorten World War II.

In non-interacting Fermi systems with imbalanced number of two different Fermions, the average momentum per fermion is higher for the majority. Adding a strong short-range interaction between different fermions may invert the momentum sharing of the two components, making the minority move faster on average than the majority. This feature is due to the high momentum distribution being dominated by short distance pairs of different type Fermions. It is a common behavior that applies to systems ranging from ultra-cold atoms at neV energies to nucleons with MeV energies. In nuclei the nucleon-nucleon tensor force makes the neutron-proton short range correlated pair (np-SRC) the dominant component contributing to the high momentum of nucleons. In light neutron-rich nuclei such as 3H, the average momentum of a proton should be higher than that of a neutron. In 3He the average momentum of the neutron should exceed that of the protons. We plan to test the above prediction experimentally by probing both the majority and minority nucleon momentum distributions of asymmetric A = 3 nuclei. We will do this by measuring the quasi-elastic 3H(e,e'p) and 3He(e,e'p) reactions in high-Q2, xB>1 kinematics where the effects of FSI are minimized. The use of mirror nuclei allows using probing the properties of the proton in one nucleus and learning about the properties of the neutron in the other. The experiment will run in 2017 at Hall-A of Jefferson-Lab, using an incoming 4.3 GeV electron beam and High Resolution Spectrometers (HRS) to detect scattered electrons and knockout protons. We will extract reduced cross-sections and cross-sections which will be used as a direct benchmark to detailed nuclear calculations in a regime they have not been tested in before.

A practice oral exam with a talk on sterile neutrinos followed by general questions.

The Earth is vulnerable to the constant threat of a catastrophic asteroid impact. In the event of an impending impact, we have a few options to protect ourselves, one of which is a nuclear detonation. Additionally, our knowledge of small but deadly asteroids is very limited. The US Government and the international community are committed to investigating and investing in efforts to safeguard the planet in the event of an impending hit. In this talk, I will describe the threat posed by asteroids and the ways by which we can mitigate it, focusing on the efforts at Lawrence Livermore National Laboratory.

Monte Carlo event generators have become indispensable tools that are widely used by modern particle and nuclear physics experiments. Such event generators typically contain a large number of parameters that need to be tuned by comparing the output of the generator with experimental data. Generating enough events to make such a comparison is often a computationally expensive task. Bayesian optimization is known to be a powerful tool in solving problems where the function has no closed-form and is expensive to evaluate, e.g. tuning the hyperparameters of machine learning algorithms. We propose treating Monte Carlo event generator tuning as a black-box optimization problem to be addressed using the framework of Bayesian optimization. In this talk, I will first give a brief introduction to event generator tuning and cover some basics of Bayesian optimization. I will then present some of our results from tuning 20 parameters of the PYTHIA8 event generator using such a Bayesian optimization approach.

The Mu2e experiment is under construction and, when finished, will search for charged lepton flavor violation (CLFV) in the form of a muon converting into an electron without associated neutrinos. An observation of charged lepton flavor violation at a rate exceeding that predicted in the Standard Model would be clear evidence for new physics. The search at Mu2e will have significant new reach in this area, with a sensitivity four orders of magnitude better than any previous CLFV experiment. I will provide a general overview of Mu2e and will discuss the work that I did on the development of the tracker, which is the component of the detector that will provide the primary momentum measurement of possible conversion electrons.

We commonly deal with very big data, and we often need to do it fast. When we want to go really fast, analyzing how algorithmic complexity affects the various parts of our program can give us clues on where to start. This talk will give a brief overview of concepts affecting runtime and include some examples.

High precision measurements of nuclear decays are one of the most precise tools for probing physics beyond the standard model. These measurements at low energies indirectly probe physics at very high energies, rivaling that of the largest accelerators, while still remaining a relatively inexpensive research program. The OLIVIA experiment is a new experiment that will perform a kinematically-complete measurement of the 8Li beta decay in 3D. While most similar measurements use optical traps, OLIVIA is based on a TPC, coupled with scintillators. The proposed setup does not require trapping 8Li ions – significantly simplifying the measurement, but dramatically increasing the statistical accuracy. I will present the proposed experimental setup, our estimated sensitivity to constrain tensor currents in electroweak theory, and my work on energy reconstruction completed this summer.

nEXO experiment is an update of EXO-200 in the future. It aims to search for neutrinoless double beta decay, thus determining if neutrino is Majorana fermion as predicted in theory. The study focuses on the detection of ionized electrons in nEXO detector, and explore how the strength of electric field in detector impacts the process of data analysis. With transform function from the design of electronics, the output waveform can be successfully transformed back to the input in simulation. In signal discrimination, the primary background is gamma with the same energy. By using the information about the charge waveform, position and time, we define input variables in TMVA to perform the event selection by BDTG method. High electric field can enhance the performance of signal discrimination and also benefit the energy resolution. The further study of these results can provide useful suggestions about some essential parameters including electric field, which can be very helpful in detector design.

Designed primarily to study decays of hadrons containing bottom quarks, LHCb's unique geometry also makes it ideal for studying the structure of the proton at both high and low x. In this talk I'll discuss searches for unobserved QCD phenomena in both of these kinematic regimes.

Neutrino flavor oscillations, as first demonstrated by SNO (2001), directly imply non-zero neutrino masses. Despite the large experimental effort put into neutrino oscillations to date, such experiments are sensitive only to mass differences, not their absolute values. Determining the absolute mass scale of the neutrino is a highly non-trivial problem requiring experimental precision into the sub-eV range. Project 8 uses a novel, radiometric approach for determining the mass scale of the neutrino. In this talk, we explore some of the efforts undertaken to improve the precision and the time-effectiveness of simulations, namely particle integration and synchrotron radiation modeling.

The Solenoidal Tracker at Relativistic Heavy-Ion Collider (STAR) Collaboration collects and analyzes experimental data from the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory. The STAR detector consists of the Time Projection Chamber (TPC), the Time of Flight (TOF) Detector, and the Heavy Flavor Tracker (HFT). The STAR detector covers full azimuthal angle at mid-rapidity with excellent particle identification. In 2014, STAR Collaboration implemented the HFT detector. The HFT detector enables precision determination of event and decay vertices. The main goal of the HFT detector is to perform precision measurement of the production of charm hadron in high energy nuclear collisions. In the meantime, it also allows clean measurements of proton. We use event plane method to calculate the coefficient of second Fourier harmonic in the azimuth of K0 particles using the data from 2014 for Au + Au at center of mass energy sNN = 200GeV in STAR Collaboration. In addition, the author studies the number-of-quark scaling law from quark coalescence model for KS0 elliptic flow and confirms that KS0 is indeed created from quark-gluon plasma. The physics motivations and detail analyses will be presented in this talk.